The invention relates to a blower or a pump having a rotor and rotor shaft which is essentially vertically disposed during operation. A housing disposed underneath the rotor and accommodates a driving motor, shaft bearings, and an oil sump. An evacuating line traverses the wall of the housing to connect a vacuum pump to the interior of this housing.
When pumps or blowers of this kind are in action, oil is atomized in the interior of the housing for the motor and bearings. This occurs inside the bearings and at inside walls of the housing if there are spinner disks. There is hence the risk of oil vapors escaping via the shaft bearing into the area of the rotor. This risk is particularly high when there is a great oil atomization caused by high rotational speeds, and when there is a low pressure in the area of the rotor. Examples include radial-flow turbo blowers for circulating gases in gas lasers and turbo molecular pumps.
In order to prevent oil vapors from entering the rotor side through the shaft bearing, it is known the connect the interior of the motor and bearing housing to a vacuum pump. If the pressure inside the housing is then maintained at a lower level, the oil vapors can no longer reach the rotor side. In this accomplishment, the vacuum pump connected to the motor and bearing housing removes the oil vapors caused by atomization by suction. In the long run, this leads to an oil loss in the motor and bearing housing.